1. Field of the Invention
The present invention relates to the field of semiconductor manufacturing and more specifically to a method and apparatus for the selective oxidation of a composite silicon/metal film.
2. Discussion of Related Art
In the fabrication of modern integrated circuits such as microprocessors and memories, selective oxidation processes are used to passivate or oxidize silicon films without oxidizing metal films contained thereon. For example, electrodes and interconnects can be made of composite silicon/barrier layer/metal films. The purpose of the barrier layer is to prevent diffusion and interaction between the silicon film and the metal film which can cause the formation a higher resistance metal silicide film. Unfortunately, during some selective oxidation processes, such as hydrogen rich (greater than 80% H2) H2/H2O ambients used to form an oxide on a silicon film but not on the metal, the barrier layer can be attacked by H2 and its integrity compromised leading to the undesired formation of a metal silicide resulting in a higher resistance composite film.
Thus what is desired is a method of selectively oxidizing a composite film in a hydrogen rich H2/H2O ambient without affecting the integrity of the barrier layer.
A method of selectively oxidizing a composite film. According to the present invention a substrate having a composite film comprising of lower silicon film, a barrier layer, and upper metal film on the barrier layer is placed into a reaction chamber. An inert gas is then fed into reaction chamber to create an inert ambient in the reaction chamber. The temperature of the substrate is then raised or ramped from first temperature to a second temperature in the inert ambient. After the temperature of the substrate is raised to the second temperature the substrate is exposed to an ambient which oxidizes the silicon but which does not oxidize the metal.